In recent years, as miniaturization, weight saving and electric power saving of electronic equipment are increasingly promoted, attention in the field of display is being focused on a semiconductor composed of an oxide IGZO including indium (In), gallium (Ga) and zinc (Zn). An IGZO amorphous oxide semiconductor film can be formed on a resin film at a low temperature, and hence, its application to light-weight portable electronic products in the future is being studied.
Heretofore, films formed of the amorphous oxide including In, Ga and Zn have been subjected to patterning by a lift-off method (K. Nomura et. al., Nature, Vol. 432, 25, Nov. 2004, pp. 488-492). In the lift-off method, however, photoresists have such low heat resistance as to melt and deform when high-temperature processing is carried out. In the step of removing photoresists, the pattern edges of deposited films may be turned up.
Japanese Patent Application Laid-Open No. 2005-258115 discloses that oxides which contain indium and zinc (i.e., IZOs) can be etched with oxalic acid, a mixed acid of phosphoric acid, acetic acid and nitric acid or a cerium (IV) ammonium nitrate aqueous solution.
However, etching solutions of the acid type as in the above etches every different coexistent film at the same etch rate, when etching an amorphous oxide semiconductor composed of an oxide including at least one of Ga and Zn, and In (i.e., IGZO, IZO or IGO).